More than 2m Muslims are currently gathering in Mecca ahead of the annual Hajj, which begins on August 19. As long as they are fit and financially able, the pilgrimage is an obligatory act of worship that followers of Islam owe to God once in their lifetime. Reenacting the faith-testing ordeals of Ibrahim (Abraham, the Biblical founder of monotheism) and his family, Muslims believe that an “accepted Hajj” will cleanse them of all their sins. Their hope is to return home as pure as the day they were born.

But until the introduction of modern transport systems, most Muslims beyond the Arab world had little expectation of completing this fifth and final pillar of Islam. Before the mid-1950s, the number of overseas pilgrims rarely exceeded 100,000 and modern Saudi institutions were still developing. Yet by the early 2000s, the total number of Hajj pilgrims had passed the 2m mark, reaching a recent peak of just over 3m in 2012.

New opportunities for pilgrimage in the jet age have put immense pressure on the infrastructure of Mecca. Hundreds have lost their lives during periodic disasters including fires and stampedes, most recently in 2015. Undoubtedly, the Saudi authorities have invested huge sums in continually seeking to improve facilities and the overall management of the Hajj. Hajj organisers and guides I have interviewed compare overseeing the pilgrimage to hosting the Olympics every year.